Methods For Controlling The Fluid Loss Properties Of Viscoelastic Surfactants Based Fluids

Abstract

It is proposed a method of treating a subterranean formation including providing a suspension of colloidal particles prior to the injection of a treating fluid based on an aqueous fluid comprising a thickening amount of a viscoelastic surfactant. The colloidal particles help to reduce fluid losses into the formation. According to a second embodiment, the treating fluid includes a hydrophobically-modified polymer, said hydrophobically-modified polymer being present at a concentration between approximately its overlap concentration c* and approximately its entanglement concentration ce. The method is particularly useful for fracturing operation in medium to high permeability formation.

Description

BACKGROUND OF INVENTION

[0001] This invention relates to compositions and methods to reduce fluid loss from viscoelastic surfactant (VES) fluids during treatment of subterranean formations such as hydraulic fracturing or wellbore cleanout operations.

[0002] Viscoelastic surfactant fluids are normally made by mixing in appropriate amounts suitable surfactants such as anionic, cationic, nonionic and zwitterionic surfactants in an aqueous medium. The rheology of viscoelastic surfactant fluids, in particular the increase in viscosity of the solution, is attributed to the three dimensional structure formed by the components in the fluids. When the surfactant concentration significantly exceeds a critical level, and eventually subject to the presence of an electrolyte, the surfactant molecules aggregate and form structures such as micelles that can interact to form a network exhibiting viscoelastic behavior. In the remaining part of this description, the term “micelle” will be used as a g...

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